Field of the Invention
The present invention relates to an image blur correction device, and a control method thereof for correcting image blur that is attributable to camera shake or subject shake.
Description of the Related Art
Panning, which is one of photographing techniques, is photographing a moving subject while a photographer swivels a camera to track motions of the subject, for example, in a horizontal direction, and a long shutter speed in the range of seconds is set to obtain an impression of dynamism in the subject. Panning generally requires skill and experience in photographing, and thus it is deemed as a hard photographing technique for a novice. A first reason therefor is that skillfully photographing a subject while moving a camera to track motions of the subject is difficult. A second reason therefor is that it is hard for a novice to know how long a shutter speed should be set to obtain an impression of dynamism in the subject. As the shutter speed becomes slower, a sense of dynamism increases because an amount of background flow increases. However, camera shake or subject shake easily occurs.
Japanese Patent Laid-Open No. 2006-317848 discloses a method in which a difference between a speed of a subject and a speed of camera movement is detected and a deviation amount corresponding to the difference is corrected using a camera shake correction function to realize panning simply. An angular velocity sensor included in the camera tracking the subject detects an angular velocity of the camera with respect to panning immediately before photographing, and a difference between an angular velocity of the subject and a panning speed of the camera is corrected.
As methods for detecting an amount of movement of a subject image on an image surface, a correlation method based on a correlation operation, block matching, and the like using detection of motion vectors, are known. In block matching, for example, an input image signal is divided into a plurality of block areas each having an appropriate size, and differences from pixels in a certain range of a previous frame are calculated in units of blocks. A block of the previous frame for which the sum of absolute values of the differences has a minimum value is searched for, and a relative deviation between screens indicates a motion vector of the block.
There is a possibility in the technology of the related art that a correct motion vector may be detected or a vector with a low degree of reliability may be detected depending on photographing conditions such as low contrast. In a case of panning with respect to a person, motions of the hands and feet are irregular, and thus motion vectors with a low degree of reliability may be detected. If motion vectors of the entire body of a person including his or her hands and feet are used, an angular velocity of a subject to be calculated may be erroneously calculated, and instead there may be a tendency for over-correction and thus subject shake may be significant.